In such systems, as the need arises, electrical power and control signals have to be transmitted from the stationary part of the system to the moving part of the system because the moving part has at least one element, for example, a control element, that has to be supplied with power during operation and that has to be controlled on the basis of the function. Alternatively, systems should also be taken into consideration in which control elements such as, for instance, capacitive actuators, have to be actuated over a certain distance.
The literature (see, for example, A. Esser, “A New Approach to Synchronize a Bidirectional DC to DC Converter for Contactless Power Supplies”, ETEP Vol. 3, No. 2, March/April 1993) discloses a method and an arrangement that allow bidirectional transmission of electrical power via articulated-arm robot joints at any desired wide angle of rotation without the need for an electrically conductive connection that runs over the rotary joint. For this purpose, an inverter forms a higher-frequency alternating voltage from direct voltage on the input side of the joint and said alternating voltage is then transmitted by means of an inductive transformer from a primary winding of the transformer on the one side of an isolating point, that is to say, an air gap, to a secondary winding that lies on the other side of the isolating point, where it is converted once again into a direct voltage. The direct-voltage-to-alternating voltage converters and alternating-voltage-to-direct-voltage converters employed in this process are configured as inverters, so that they can be operated bidirectionally and consequently the power flow is reversible. A capacitor that was charged downstream from the isolating point on the secondary side can be discharged by transmitting the power back to the primary side via the isolating point.
Control elements are also fundamentally known. One example of this is the piezo element that is employed as a capacitive actuator in automobiles, aircraft or other technical devices where components have to be moved at a high frequency and medium actuating force. This can be done by installing control members individually or in the form of groups of several control members. Regarding the latter, German patent application DE 199 27 087 A1 describes a method and a device for charging and discharging several piezo electric elements. By means of appropriately actuated charging and discharging switches, groups comprising one or more piezo electric elements can be charged or discharged independently of each other. During the power exchange between the capacitor on the secondary side—which, as a buffer capacitor, has a larger capacitance than the piezo elements, whereby both capacitors are generally charged at different voltages—the rise of the charging and discharging current is limited by a winding and its magnitude is set by periodic switching, also referred to as cycling. This cycling is done by switching high-frequency semiconductor switches on and off, whereby the charging and discharging current stored in a winding 2 generates a high switching loss in the semiconductors during the switching. Another drawback of this method and arrangement is the double wall and the storage of power in the moving system. The alternating voltage or the alternating current inductively transmitted via the isolating point, i.e., the air gap, is rectified in the moving system and the power is stored in a buffer capacitor, usually configured as an electrolyte capacitor, that is even considerably larger than the capacitor of the piezo element. Then one or more piezo elements are charged with current cycled from the buffer capacitor at a high frequency. In contrast, it is desirable to have a method that supplies the power transmitted at a higher-frequency voltage or higher-frequency current to the piezo electric elements via the isolating point without any intermediate storage.
However, nowhere does this publication indicate how the piezo electric elements are to be actuated, particularly when the latter are arranged on the moving part of a system consisting of a stationary part and a moving part. Furthermore, in the case of special moving systems that are exposed to vibrations and/or high speeds, the problem arises that certain electric components are no longer suited for these operating conditions. Assuming, for instance, that the device is deployed in the area of the rotor shaft and the rotor head of a helicopter, then the high mechanical load makes it fundamentally impossible to use electrolyte capacitors. Particularly in applications involving rough ambient conditions such as high and low temperatures as well as large centrifugal acceleration forces on the moving system, for example, on the rotor head of a helicopter, operations using electrolyte capacitors are only possible at considerable risk.
World patent WO-A-0048299 describes a device for converting higher voltages of the type employed, for example, in trains or streetcars, into low direct voltages or alternating voltages, as is necessary for the operation of lighting systems or air-conditioning units. For this purpose, a transformer is employed that galvanically separates the primary and the secondary circuits from each other in a known manner. However, no provisions are made for transmitting power and control signals from a static part to a rotating part of a system or else for operating an actuator control element on the rotating part of the system by means of the transmitted signals.
U.S. Pat. No. 5,709,291 discloses a device with which power is transmitted contactless to a moving device, for instance, from a work station to the next moving pallet. For this purpose, a bar-type transformer is employed that allows linear movements of the moving device. The voltage that is transmitted by this transformer to the moving device is at first rectified and then used to charge a battery that is carried on the moving. device. The battery is used to supply a motor that is carried on the moving device. Influencing the motor controls by utilizing the transformer is not described here. Moreover, this system is not suitable for use in the area of the rotor shaft and the rotor head of a helicopter since the use of batteries in the area of the rotor head is not possible due to weight and space considerations. Requirements calling for a wide useful temperature range and for resistance to high centrifugal acceleration forces cannot be met when batteries are used.